The invention relates to the field of displacement sensors and, more specifically, displacement sensors used in motor vehicle devices or equipment, for example in braking devices or power-assisted braking devices.
Displacement sensors are already well known in principle. Said linear sensors, for measuring an axial path of a part sliding in an axial direction in a frame, comprise a so-called mobile part cooperating with a so-called fixed part. Said mobile part of the sensor comprises:                a longitudinal element cooperating with said part so that any translation of said part causes an axial translation of said mobile part; and        a magnetic field source integral with said longitudinal element at its end so that any displacement of said upper end causes the displacement of said source.        
Said fixed part comprises a receiving means for said magnetic field arranged opposite said source and capable of sending a signal known as the primary signal, depending on the axial path of said part, to a transducer capable of converting said primary signal into an electrical signal transmitted to a connector making it possible to transfer said electrical signal to an external electrical circuit.
The displacement sensors of the prior art have several types of problems:                firstly, the sensors may have a problem of restricted space, to the extent that they have to be positioned in a relatively small space, in particular in said axial direction corresponding to the direction of displacement of the mobile part sliding in the fixed frame;        moreover, the sensors may have problems of reliability and/or of calibration; and        finally, the sensors may present difficulties in terms of mounting, in particular taking into account the restricted access for said mobile part.        
More specifically, these problems are posed even more acutely when said sensors have to be installed on braking devices or power-assisted braking devices.
A first subject of the invention consists of a linear sensor permitting the problems posed to be solved.
A second subject of the invention consists in using such a sensor in motor vehicle devices or equipment, for example in braking devices or power-assisted braking devices.
According to the invention, the linear sensor is provided for measuring an axial path L0 of a part sliding in an axial direction in a frame with a transverse wall perpendicular to said axial direction, comprising a part known as a mobile part cooperating with a part known as a fixed part, said mobile part comprising:                a longitudinal element cooperating, at its so-called lower end, with said part using a first connecting means, so that said lower end is mobile in an axial path following that of said mobile part, any translation of said part causing an axial translation of said lower end, and a displacement of said longitudinal element causing a corresponding displacement of its so-called upper end; and        a magnetic field source integral with said longitudinal element at its upper end, using a so-called second connecting means, so that any displacement of said upper end causes the displacement of said source, said fixed part comprising a receiving means for said magnetic field opposite said source and capable of sending a signal known as the primary signal, depending on said axial path, to a transducer capable of converting said primary signal into an electrical signal S transmitted to a connector, making it possible to transfer said electrical signal S to an external electrical circuit.        
The linear sensor is characterized in that said fixed part comprises an angular redirection means cooperating with said longitudinal element using an angled part and thus transforming said axial path of said lower end into a radial path of said upper end, in a direction known as the radial direction which is typically perpendicular to said axial direction so that said sensor has a low axial spatial requirement, typically less than 3L0.
The linear sensors according to the invention solve the problems posed. More specifically:                on the one hand, they have a very low axial spatial requirement, to the point of possibly not requiring their own axial spacing;        on the other hand, they may be tested and calibrated before being installed at the junction between said frame and said mobile part sliding in said fixed frame; and        finally, their spatial requirement, which is essentially radial, facilitates their assembly at the junction between said frame and said mobile part.        